Genome editing, gene drives, and synthetic biology: Will they contribute to disease-resistant crops, and who will benefit?

Ensuring the access of small-scale farmers to products and potential benefits from genetic engineering (GE) technologies for agriculture will require concerted investment and research by public institutions worldwide and particularly in low- and middle-income countries.
 

This was a key conclusion of a new review paper describing cutting-edge GE applications that offer exciting options to enhance the disease and pest resistance of important food crops and the ecological sustainability of cropping systems.
 

The technologies include gene editing (site-specific changes to DNA in a genome), gene drives (greatly enhancing or reducing frequency of genes that affect insect or pathogen reproduction), and synthetic biology (re-design or construction of biological devices, for example chromosomes or organelles).
 

Authored by international experts in policy, socioeconomics, and biological science, the new paper outlines potential uses of the technologies, particularly to address problems that affect resource-poor farmers or consumers, such as the viruses that attack cassava, the Striga weed that is a parasite of maize, or the fungal pathogen of groundnut that produces deadly toxins.
 

A weak capacity for research and development in many countries, combined with a small and declining public investment, raises questions about those nations’ ability to develop and deliver high-quality GE technologies or realize their benefits.
 

“The concern is that farmers not served by leading companies, who are developing the technologies, will be unable to obtain new, resistant crop varieties or other products of these technologies,” said Kevin Pixley, director of the genetic resources program of the International Maize and Wheat Improvement Center (CIMMYT) and first author of the new paper.
 

The technologies have already proven effective for controlling bacterial, fungal, and viral plant pathogens, as well as insects that transmit them. For example, GE approaches to control cassava brown streak disease and cassava bacterial blight—for which there are few or no known sources of resistance in cassava itself—appear on track to produce resistant versions of cassava.
 

Future gene drive technologies that can be kept within specific areas and reversed if needed may offer ways to control insects that carry plant diseases or weeds that damage crops, and synthetic biology could someday create plants that are immune to invading viruses.
 

Institutional forces (arrows) alter the balance of public vs private research / development investments and the relative emphasis on low vs high value crops, factors that help determine who benefits (resource-poor vs wealthy farmers?) from the application of advanced technologies in crop breeding. (Figure: Nancy Valtierra/CIMMYT)
 

“The private sector is likely to invest mainly in major crops and major traits that will bring them profits, so work on minor, perennial, clonal, or staple food crops of lower-income countries may suffer,” said José Falck-Zepeda, senior research fellow and leader of the policy team in the program for biosafety systems of the International Food Policy Research Institute (IFPRI) and a co-author of the review paper.
 

Many countries are still deciding whether and how they will regulate new GE products. The new paper explains how key factors including the cost and complexity of complying with biosafety regulations will shape the potential distribution of the technologies and products, determining which institutions undertake the related research and, as a result, which traits and crops are studied.
 

Civil society concerns regarding GE technologies and how or by whom they are deployed add important considerations to the complex questions surrounding the use of GE products.
 

“Realizing the potential of GE crops will require investments and policies for research, intellectual property regimes, and regulatory frameworks,” say the authors, “and societies must also address legitimate concerns about their responsible stewardship, agroecological sustainability, and equitable access to associated benefits.”
 

An open-access version of the full paper is available online:

Pixley, K.V., J.B. Falck-Zepeda, K.E. Giller, L.L. Glenna, F. Gould, C.A. Mallory-Smith, D.M. Stelly, and C.N. Stewart. 2019. Genome editing, gene drives, and synthetic biology: Will they contribute to disease-resistant crops, and who will benefit? Annu. Rev. Phytopathol 57:8.1–8.24.